added maplibre-gl-legend and mapbox-gl-legend

[JinIgarashi]

@ubukawa @hfu @naogify Could you merge this PR to main?

Description

Add features related to #95

The preview will be like the below screenshot. I hope this will help edit style.

Note. This feature is only available for maplibre and mapbox. It does not support geolonia.

Type of Pull Request

• [x] Adding a feature
• [ ] Fixing a bug
• [ ] Maintaining documents
• [ ] Others ()

Verify the followings

• [x] Code is up-to-date with the main branch
• [x] No build errors after npm run build
• [x] No lint errors after npm run lint
• [x] No errors on using charites help globally
• [x] Make sure all the exsiting features working well
• [x] Have you added at least one unit test if you are going to add new feature?
• [x] Have you updated documentation?

Refer to CONTRIBUTING.MD for more details.

[JinIgarashi]

@ubukawa Thank you for consideration. It is no problem to use my plugin without any copyright text.

[ubukawa]

Thank you @JinIgarashi for your kind clarification. I am ready to merge this.

Dear @hfu and @naogify , please let us know if you have any comments. I will wait for a few days just in case, and merge this PR to main. Thank you. Have a nice day!